Poseidon recommends the o-rings on the Fischer connectors be lubricated, but does not specify the lubricant. Based on our many years of experience with Fischer connectors on several other brands of diving computers, Dive Gear Express recommends using DeOxit GN5. The DeOxit will keep the o-rings sufficiently lubricated plus also clean and protect the low current contacts in the connectors. Some people prefer to fill the connector with a liberal amount of pure unscented mineral oil (aka paraffin oil or white oil), although it's a bit messy. We also specifically recommend avoiding any of the various silicone lubricants commonly used in diving applications as we suspect they are not compatible with the o-ring material in the connector.